Observation of coupled plasmon-polariton modes of plasmon waveguides for electromagnetic energy transport below the diff
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Observation of coupled plasmon-polariton modes of plasmon waveguides for electromagnetic energy transport below the diffraction limit Stefan A. Maier*, Pieter G. Kik, Mark L. Brongersma and Harry A. Atwater Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA Sheffer Meltzer, Ari A.G. Requicha, and Bruce E. Koel Laboratory for Molecular Robotics University of Southern California, Los Angeles, CA 90089, USA *e-mail: [email protected]
Abstract We study the influence of optical near-field interactions on the dipole surface plasmon resonance of Au nanoparticles in closely spaced particle arrays using finite-difference timedomain simulations. In particular, the resonance energies of the collective plasmon-polariton modes are determined for longitudinal and transverse polarization for different particle array lengths and inter-particle spacings of 50 nm Au spheres in air. The obtained results are set in context with recent publications suggesting the possibility to use ordered arrays of closely spaced noble metal nanoparticles as plasmon waveguides for electromagnetic energy below the diffraction limit of light. Introduction The optical properties of metal nanoparticles have been the focus of intense research for a number of years [1]. From work on single noble metal nanoparticles, it is well established that light at the dipole surface plasmon frequency interacts strongly with metal nanoparticles and excites a collective electron motion, or surface plasmon-polariton [2]. These plasmon resonances are typically in the visible or infrared part of the spectrum and exhibit plasmon decay times of a few femtoseconds [1]. For particles with a diameter D much smaller than the wavelength λ of the exciting light, plasmon excitations produce oscillating dipole fields. Whereas until recently most work has focused on the optical properties of disordered arrays of large numbers of particles, advances in particle synthesis and fabrication now allow for an investigation of the optical properties of ordered arrays of metal nanoparticles and the effects of particle interactions on the plasmon resonance. Since each excited nanoparticle with a diameter D
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